1. Field
The present invention relates to a backlash adjusting device of a cam driving gear mechanism in which members occupying the outside of an internal combustion engine can be reduced in number and miniaturized.
2. Description of the Related Art
Patent Document 1 (Japanese Patent No. 4381971 (FIG. 1, FIG. 2, and FIGS. 6 to 8)), for example, shows a mechanism capable of adjusting a clearance between an idler drive gear (driving gear) and an idle gear (driven gear) meshing with the idler drive gear, that is, a backlash in a cam driving gear mechanism for transmitting rotational power to the valve gear of an internal combustion engine, with a shaft supporting the idle gear formed as an eccentric shaft whose angle of rotation can be fixed at a predetermined angle of rotation.
The mechanism shown in Patent Document 1 has a structure in which an adjusting portion for adjusting the angle of rotation of the eccentric shaft and a fixing portion for fixing the angle of rotation of the eccentric shaft at a predetermined angle of rotation are both exposed to the outside of a cylinder block, and further the fixing portion fixes a flange portion of the adjusting portion with a bolt. Thus, an adjustment space for the flange portion needs to be secured on the outside of the cylinder block, which results in poor space efficiency on the outside of the internal combustion engine, and may consequently invite an increase in size of the internal combustion engine.